Embedded systems can be used in a variety of applications, including providing monitoring, sensing, control, or security functions. Such embedded systems are generally tailored to specific applications, according to relatively severe constraints on size, power consumption, or environmental resilience.
One class of embedded system includes sensor nodes, such as for sensing or monitoring one or more physiologic parameters, or for other applications. A sensor node having wireless communication capability can be referred to as a Wireless Sensor Node (WSN). A sensor node located on, nearby, or within a body of a subject can be referred to as a Body Area Sensor node (BASN) or Body Sensor node (BSN). Sensor nodes can provide significant benefit to care providers, such as by enabling continuous monitoring or logging of physiologic information, facilitating automated or remote follow-up, or providing one or more alerts in the presence of deteriorating physiologic status. The physiologic information obtained using a sensor node can be transferred to other systems, such as used to help diagnose, prevent, and respond to various illnesses such as diabetes, asthma, cardiac conditions. Many nodes, among other devices, require hardware having ultra low power (ULP) consumption requirements, such as to support long system lifetimes on stringent energy budgets. Many devices require a stable clock source for precise data sampling, RF modulation, and keeping time to reduce the cost of re-synchronizing to other radios, among other reasons.